rebuilt block but low compression. why...?

[99 gst spyder]

With a normal operating temp, I had 90-85-110-90 across the board. Built just the block. Block has been hone clean and resurface with used je piston, eagle rod, new je piston rings, new head gasket, and all new bearings. Also cleaned and polished stock crank.

Another problem also, when I take my COP off the valve cover, I can see oil/fuel mixture lying next to the spark plug well. It smell like fuel and oil mix. Some one tell me why? Outside of the car smells like fuel while idling too.

I do have a little coolant leak but not sure where it's coming from yet, still looking into it.

Car runs fine. just not sure why i have low compression. i did gap the piston rings and make sure the gaps aren't over lapping each other.

I may have miss some things but this the start.

Thanks in advance.

 

[bryanwheat]

Did you have any valve work done? I would do a leakdown test, that is very low for a fresh engine.

 

[99 gst spyder]

Did you have any valve work done? I would do a leakdown test, that is very low for a fresh engine.

No valve work done, just replace the valve seals and 272 cams. I was also thinking about a leak down test too but I've heard new built motor could begin with low compression and work it's way up but I'm not sure.

Anyone want to chip on the oil/fuel mixture?

thanks

 

[Seamus]

Are you sure you are doing the comp test correct? Is the throttle wide open. A lot of local guys have been thinking they have hurt motors lately, and they aren't doing their tests correctly.

 

[99 gst spyder]

Are you sure you are doing the comp test correct? Is the throttle wide open. A lot of local guys have been thinking they have hurt motors lately, and they aren't doing their tests correctly.

I'm pretty sure I did it correctly. I had all the spark plug out, took the mpi fuse out, and wot on every test across the board. I do have oil on the threads on all the spark plug.

Any help on the fuel/oil mixture?

 

[WES_393]

If there is fuel in the spark plug well then you have a leak somewhere near the fuel rail and it's spraying under the COP. Either that or your oil is getting washed by gas making past the rings and into the crankcase, then back up into the spark plug well from a cracked valve cover or leaking valve cover gasket. At this point all you can do is run a leak down test. That will tell you what is leaking. What head gasket did you use? What size pistons/bore?

 

[99 gst spyder]

If there is fuel in the spark plug well then you have a leak somewhere near the fuel rail and it's spraying under the COP. Either that or your oil is getting washed by gas making past the rings and into the crankcase, then back up into the spark plug well from a cracked valve cover or leaking valve cover gasket. At this point all you can do is run a leak down test. That will tell you what is leaking. What head gasket did you use? What size pistons/bore?

Okay, it was bore .020 over before I had the block, so I had the machine hone it out with .020 over piston rings.

There is no oil/fuel mixture in the well at all just sitting on the surface.

Car doesn't smoke at all, only on cold start up which I think it's normal.

 

[okm12346]

Did you bleed the lifters?

 

[keltalon]

i did gap the piston rings and make sure the gaps aren't over lapping each other.

I may have miss some things but this the start.

Thanks in advance.

I mean just a though did you make sure you put the compression rings in the right order and not mixed the top up with the second ring? Also did you put the dot on the ring facing up?

 

['97boostinGST]

How many miles on rebuild?

 

[Awesomewheeldrive]

Did you atleast lap your valves? Everytime i take a head apart i lap the valves so they seat properly. Also, did you have the piston rings cut properly? Another possible issue could be that all the gaps in your rings are facing the same direction. But these are worst case scenarios for your problem. Id check to see if your spark plugs are seating correctly if you say there is fuel under your COP set up.

what head gasket are you using? If your using an mls you need to make sure you had enough decked off.

 

[Cdc1221]

Did you have the head surface recut? Just a small scratch can cause problems

 

[jimbob_843]

Now the machine shop honed it out for you? Did you bring them the pistons to do so? And who gapped the rings? Ive been to a shop that said sure i can bore it 20 over for ya, no pistons no nothing. The correct way is to bore each cylinder to its corresponding piston and then gap the rings to the cylinder.

 

[99 gst spyder]

Did you bleed the lifters?

Yes I did.

Did you atleast lap your valves? Everytime i take a head apart i lap the valves so they seat properly. Also, did you have the piston rings cut properly? Another possible issue could be that all the gaps in your rings are facing the same direction. But these are worst case scenarios for your problem. Id check to see if your spark plugs are seating correctly if you say there is fuel under your COP set up.

what head gasket are you using? If your using an mls you need to make sure you had enough decked off.

I'm using felpro hg. I'm not quit sure on the overlapping part. I'm pretty sure I had the rings order and gap and they aren't facing the same direction.

Did you have the head surface recut? Just a small scratch can cause problems

I didn't surface the head.

Now the machine shop honed it out for you? Did you bring them the pistons to do so? And who gapped the rings? Ive been to a shop that said sure i can bore it 20 over for ya, no pistons no nothing. The correct way is to bore each cylinder to its corresponding piston and then gap the rings to the cylinder.

I brought the pistons, rods, and block to the shop, they measured everything and cleaned them all. They said the block is already bored .020 and it's still in good condition so they just honed it out.

I gap/file the rings myself. Just tell me what are the gap for the je piston and rings just so I'm clear I gap them right.

What about the oil rings, anyone want to tell me the correct way to see if I did it right.

 

[simple jake]

How many miles on the build and what was your break-in procedure for the block?

 

[jimbob_843]

You have to search their site for specs.
How did you gap the rings? If you dont mind me asking.

 

[WES_393]

The engine shouldn't be smoking upon startup. Maybe a puff or two if you have leaky valve stem seals, but if your seeing a nice little cloud behind the car while it warms up, that's not a good sign.

There is no way to see if you gapped the pistons correctly now, you would have to pull them out again. Typical piston ring gap for turbo engines and forged pistons is between .015 and .025. Some run it smaller, some run them wider, but the important thing is that they all be exactly the same and the top ring gap be as close to 180* from the second ring gap. It would be best to find the specs for your pistons though as different pistons and rings require different piston to wall clearances and end gap sizes.

 

[Diamond Star Werks]

I'm pretty sure I did it correctly. I had all the spark plug out, took the mpi fuse out, and wot on every test across the board. I do have oil on the threads on all the spark plug.

Any help on the fuel/oil mixture?

The fuel oil mixture is probably from an oil leak. In building an engine you will always get gas in the oil as you have to give it time for the rings seat and seal properly. This is one reason why some ppl change their oil after the first run of a rebuilt engine. What was the condition of the head you put on? Did you have it checked at all? Its never a good idea to put a used head on without having it checked unless your 100% its good or heard it run on the car it used to be on. You can try washing your cylinders. That might help the rings seal up if they are not doing so properly.

 

[99 gst spyder]

How many miles on the build and what was your break-in procedure for the block?

Less then a hundred miles for sure. I've been just driving it around the block and to the gas station only. Driving normally, not wot pulls or anything.

You have to search their site for specs.
How did you gap the rings? If you dont mind me asking.

I had file the top ring to .021 and .025 for the second ring.

The fuel oil mixture is probably from an oil leak. In building an engine you will always get gas in the oil as you have to give it time for the rings seat and seal properly. This is one reason why some ppl change their oil after the first run of a rebuilt engine. What was the condition of the head you put on? Did you have it checked at all? Its never a good idea to put a used head on without having it checked unless your 100% its good or heard it run on the car it used to be on. You can try washing your cylinders. That might help the rings seal up if they are not doing so properly.

The head only has 80k miles on it, and it was running fine before the swap to the built block. I didn't have the shop check the head out yet. Yeah I've heard that compression can be a little low after a build then the rings will slowly seat itself in while breaking in the motor but im not sure on this though.

What do you mean by washing my cylinders?

 

[stevecbr929]

How many miles on the build and what was your break-in procedure for the block?

I would drive it a bit and seat the rings. I rebuilt my 2g a while ago and checked the compression right after getting my car buttoned back up with disappointing initial results. I was really really careful doing the build and was sure I hadn't slipped up anywhere, so was freakin out with the lower than expected numbers.

Then I took her out just because it had been down for too long and I wanted to see if just seating in the rings would make a difference. Big difference for sure. I didn't do any full throttle pulls, just 3rd gear - put a decent load on it, shifted to 4th, then lifted. I repeated this for a few miles, went home, dumped oil/filter let it cool and ran compression test again with great results.

I did have head decked/milled at a local shop while it was off though & had them do a leakdown just to be sure I wouldn't have any issues when it went back on the block.

Take her for a drive - good luck.

 

[99 gst spyder]

I would drive it a bit and seat the rings. I rebuilt my 2g a while ago and checked the compression right after getting my car buttoned back up with disappointing initial results. I was really really careful doing the build and was sure I hadn't slipped up anywhere, so was freakin out with the lower than expected numbers.

Then I took her out just because it had been down for too long and I wanted to see if just seating in the rings would make a difference. Big difference for sure. I didn't do any full throttle pulls, just 3rd gear - put a decent load on it, shifted to 4th, then lifted. I repeated this for a few miles, went home, dumped oil/filter let it cool and ran compression test again with great results.

I did have head decked/milled at a local shop while it was off though & had them do a leakdown just to be sure I wouldn't have any issues when it went back on the block.

Take her for a drive - good luck.

Thanks for the reply. That just made my day. Lol. Hopefully it'll just be like your story.

How often should I change oil since there oil and fuel mix?

Thanks again.

 

[bryanwheat]

I usually change the oil after the first initial startup and run. I let it run for about ten minutes to get the engine warmed up to operating temp, check for leaks than shut it off, change the oil and drive it for about 50 miles and change it again. From there i will change it after a few hundred. At this point the engine should be broken in pretty well and you will see less and less break in material. You want to put a good load on the engine while breaking it in. I usually just do low boost high gear low speed pulls.

 

[99 gst spyder]

I usually change the oil after the first initial startup and run. I let it run for about ten minutes to get the engine warmed up to operating temp, check for leaks than shut it off, change the oil and drive it for about 50 miles and change it again. From there i will change it after a few hundred. At this point the engine should be broken in pretty well and you will see less and less break in material. You want to put a good load on the engine while breaking it in. I usually just do low boost high gear low speed pulls.

What exactly do you mean good load?

 

[bryanwheat]

What exactly do you mean good load?

A high load would be when you are in a high gear at a low speed. The engine is making power but not instantly pulling thru the rpm band like if would in the lower rpm's.

 

[stevecbr929]

I usually change the oil after the first initial startup and run. I let it run for about ten minutes to get the engine warmed up to operating temp, check for leaks than shut it off, change the oil and drive it for about 50 miles and change it again. From there i will change it after a few hundred. At this point the engine should be broken in pretty well and you will see less and less break in material. You want to put a good load on the engine while breaking it in. I usually just do low boost high gear low speed pulls.

Yup, exactly what he said..